Small Signal Amplifiers Response to Questions and Comments

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Күн бұрын

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@jroelofs12 6 ай бұрын

Never think a real good teacher can’t hold his students attention for more than a few minutes. Although in my 7th decade with no tech science education you finally made me understand the topic (required for my HAM license.) Best regards from the Netherlands.

@ramon2190 2 ай бұрын

Another important function of that coupling capacitor is that mic voltage by itself wouldn't be enough to trigger the transistor. Well you could say that's why there is a voltage divider at the base and it's true but still you would need a way to make the ac from the mic high enough (around 0,7V or higher) and the coupling cap does exactly that by staying charged at voltage divider level, which adds a positive offset to the mic ac. I guess that's why they are called coupling capacitors and maybe ac coupling is actually shifting up or down an ac and not just blocking dc, maybe they are two sides of the same coin, at least in this case I think it is. And thanks for the lectures, I am currently reviewing these fundamentals and I find them very useful.

@Bobsmith-yf9oy 8 ай бұрын

I did this stuff exactly 50 years ago in a lecture theatre at Manakau Tech. The teacher basically read from the text and drew the necessary things, but wasn't feeling it like we saw here. There was no connection, just repetition. I wonder if he actually understood the material? By contrast, this time he seemed to feel those voltages, electron flows and AC signals. If this, then that, because... - that is just brilliant and imparts true knowledge to the class. How i wish this man had been our teacher. I got more from this vid than prolly 10 hours of formal amp design in 1974. Am going to run this up on a breadboard with a 2n2222 or BC54-something and see the output signal change, based on calculations and experiment. And I'm sure it'll work better than those labs at MTI. Thank you, I've subscribed and want lots more!

@axle.student 4 күн бұрын

Thank you. 2 exceptionally well done videos, and very well explained. Learned more about small class A here than weeks reading on the internet:) Old video[s] (part 1 and 2), but very relevant for me :) > 2 questions: 1. Electrolytic (polarized) or Ceramic (unpolarized)? ( I would expect ceramic, but I have seen people use polarized as well.) . 2. We start with an AC signal +|0|- then end up with a + DC voltage all the way on output +0|+4|+8. This DC offset confuses me when I think of a speaker requiring AC. My brain is expecting -4|0|+4? What am I missing, or what terms (keywords) should I look for for more study?

@rosi6144 Жыл бұрын

The diode also has a 0.7 voltage drop so everything beneath 0.7 volts wil not be amplified

@Bobsmith-yf9oy 8 ай бұрын

Yup, he said this and even drew a little graph, remember? He started at 0.5V...

@samconomo3726 12 күн бұрын

Thanks,so good

@ΚωνσταντίνοςΛαζαρίδης-ξ9ι 2 ай бұрын

thank you!

@burmansound 29 күн бұрын

How does the base pulldown resistor cause negative feedback? Don't you need to feed the output back into the input for that?

@Old_Coder 10 ай бұрын

Would not a diode rectify that part of the AC signal above 0.7v ( if the input was say 2v peak to peak) So there would be an amplified output of the input?

@artistentertainment366 3 ай бұрын

I know that the alternating current oscillates, but in the video you showed us that the output of your amplifier the current is oscillating in between zero volt and an example of ten volts. What can you say about that??.thank you

@Sergiuss555 4 ай бұрын

What if you don't know the frequnecy of the signal from the sensor? What if it's DC, e.g. thermometer?

@edidiong1234 6 ай бұрын

Interesting.

@kaze2827 7 ай бұрын

Shouldnt the capacitor be polarized? Or the non polarized ones would work just fine?

@luekbaja 9 ай бұрын

Why is the AC coupling capacitor added at the emitter to increase gain if the primary purpose of most of the other additional components are to decrease gain and decrease the significance of the transistor's natural hFE? If this bypasses the emitter resistor why is it needed in the first place?

@flurng 8 ай бұрын

Keep in mind that the signal current is a.c., but the working (supply) current of the amplifier circuit is d.c. So, the bypass capacitor does bypass the signal current, but ONLY the signal current: the d.c. supply current still "sees" the emitter resistance, so it continues to maintain the proper circuit bias.

@maheshm2135 6 ай бұрын

Instead of capacitor can we use transistor

@MarkPoullos-v4f 2 ай бұрын

Auto focus, suggestion, shut it off. The depth of field is quite shallow, so it may not be necessary. Additionally, you can put a device in the foreground like a carousel so that it locks the auto focus. However, this would probably be distracting from the video. Some modern cameras have controls on the auto focus range. Especially the modern digital cameras that use a matrix algorithm to control the focus.